Method of heat treating metallic pipes and tubes



Nov; 24, 1942. 5 G. MURRAY HAL 2,303,132

METHOD OF HEAT TREATING METALLIC PIPES AND TUBES Filed Nov. 20, 1940 Y,hwnfarx M44504 i MUBGVKM' Pet-052mg 6. /25,

Patented Nov. 24, 1942 METHOD OF HEAT TREATING METALLIC PIPES AND TUBESMalcolm G. Murray, Ellwood City, and Frederick G. Raab, Beaver, Pa.,assignors to National Tube Company, a corporation of New JerseyApplication November 20, 1940, Serial No. 366,484

1 Claim.

This invention relates to the heat treating of metallic pipes and tubesand more particularly to plugs for closing the ends of the same tominimize scaling n the inside surfaces as the result of annealing forlong periods of time.

After the heat treating or annealing of metallic pipes and tubes, theinterior scale is difficult to remove and frequently requires the use ofsandblasting apparatus, which greatly extends the pickling or cleaningtime. In the case of small tubes, the ends may be pointed and thisprovides and inexpensive and satisfactory closure. With larger tubes,however, pointing is not satisfactory and the ends of the pipes arefrequently plugged with various fire clay compositions. These fire claycompositions shrink considerably on drying and fail to provide effectiveseals.

It is among the objects of the present invention to provide a method ofheat treating metallic pipes and tubes which will eifectively eliminateinterior scaling resulting from the application of heat.

Another object is to provide a method of the class described which isinexpensive and one which may easily be practiced.

The foregoing and other objects will be more apparent after referring tothe single drawing which is a longitudinal sectional elevationillustrating a device which may be used to practice the method of theinvention and is shown as applied to both ends of a conventional pipe.

Referring more particularly to the drawing, the numeral 1 designates apipe which it is desired to heat treat. According to the teachings ofthe present invention, the pipe I prior to the heat treating operationis supplied at both of its ends with a plug 2 which is composed of steelwool. This material can be easily forced into the ends of the pipe toform a tight plug due to its resiliency. Due to the fact that the steelwool has the same thermal coefilcient of expansion as the steel tube,oxidation causes it to increase somewhat in volume so that it does notshrink away from the walls of the tube in the manner of the fire claycompositions referred to hereinbefore. The coarse nature of the steelwool plug 2 permits the escape ofair from the interior of the pipeduring the heating period, while during the period the pipe is cooled,the inrush of air is impeded and an appreciable part of the oxygenfiltered out by the large exposed surface of the steel wool.

According to a permissive modification, there may be used in lieu of thesteel wool described hereinbefore metallic wool made from Stainlesssteel or alloys of the Nichrome class. These alloys have a coefficientof expansion substantially greater than that of steel, and while thecost thereof is higher they could be reused several times, thusresulting in economy.

While We have shown and described one specific embodiment of ourinvention, it will be seen that We do not wish to be limited exactlythereto, since various modifications may be made without departing fromthe scope of the invention as defined in the appended claim.

We claim:

The method of heat treating metallic pipes and tubes which includesplugging the ends thereof in a substantially tight manner with metallicwool having a thermal coefiicient of expansion not materially less thanthat of the metal of thepipe or tube being treated, exposing the saidpipe or tube to heat, permitting the pipe or tube to cool, and removingthe metallic wool from the ends of the cooled pipe or tube.

MALCOLM G. MURRAY. FREDERICK C. RAAB.

